1. Field of the Invention
The present invention relates to an image forming apparatus adapted for copiers, facsimiles, printers and the like, and more particularly to color image forming apparatus that use an intermediate transfer member to transfer toner images to a recording medium.
2. Description of the Related Art
Conventionally, in the field of image forming apparatus implementing an intermediate transfer member, such as an intermediate transfer belt, the intermediate transfer member moves in one direction with a surface thereof facing and contacting an image carrier. Toner images sequentially formed on the image carrier are then transferred from the image carrier to the intermediate transfer member superimposing one upon the other. The superimposed toner images are then transferred to a recording medium, such as a paper sheet. After the superimposed toner images are transferred to the recording medium, the surface of the intermediate transfer member is cleaned by a cleaning device mounted adjacent the intermediate transfer member to prevent contamination of subsequent images to be formed thereupon.
Also, there has been known an image forming apparatus, in which a plurality of pages of superimposed toner images are formed on the intermediate transfer member when the size of an original image is small, such that through-put of the apparatus (the number of prints per unit time) increases.
In such an image forming apparatus, in which toner images sequentially formed on the image carrier are transferred to an intermediate transfer belt one upon the other, the transferred toner images may be damaged if a given ratio of linear velocity of the image carrier and the intermediate transfer belt changes during the transfer of toner images from the image carrier to the intermediate transfer belt (hereinafter such a transfer is referred to as a belt transfer). For example, the transferred toner images may blur, or a lateral white stripe where no toner is transferred may be formed on the transferred toner images.
Generally, such a change in the ratio of the linear velocity of the image carrier and the intermediate transfer belt may be caused by sudden load changes on the driving system of the image carrier and/or the intermediate transfer belt. Such load changes often occur when a cleaning device used to clean the belt, such as a rubber blade, contacts or separates from the intermediate transfer belt.
To avoid damaging transferred toner images during a belt transfer, it is desirable to clean the intermediate transfer belt when the belt transfer process is not being performed. In other words, the belt transfer is not performed when the cleaning process is being performed. However, this decreases through-put (the number of prints per unit time) of the apparatus when images are continuously formed, because a belt transfer for a next print is not started until the cleaning process of the intermediate transfer belt for the preceding print is completed.
Therefore, a need exists for an improved image forming apparatus that times the cleaning process for the intermediate transfer member with the belt transfer process to maximize through-put when continuously forming images while avoiding toner image damage or deterioration when transferring toner images from an image carrier to an intermediate transfer member.